<?php 
if(!isset($workStatus))
  $workStatus = isset($_POST['$workStatus']) ? $_POST['$workStatus'] : null;
?>
<select name="workStatus">
  <option value="-1">--</option>
  <option value="1" <?php echo ($workStatus == 1) ? 'selected="selected"' : null;?>>есть в наличии</option>
  <option value="2" <?php echo ($workStatus == 2) ? 'selected="selected"' : null;?>>сделаю на заказ</option>
  <option value="3" <?php echo ($workStatus == 3) ? 'selected="selected"' : null;?>>работа продана</option>
</select>